The present invention relates, in general, to flow meters and, in particular, to a new and useful dedicated correlator which operates to establish maximum correlation between a delayed and undelayed signal supplied from two spaced apart sensors which sense noise signals coming from a fluid flow.
The use of correlation techniques for establishing fluid flow and other operator parameters is disclosed in U.S. Pat. No. 4,019,038 to Critten et al. According to that disclosure, an ultrasonic signal is passed through a flow of fluid at two spaced locations along the flow direction. The amount of correlation between these two signals where one signal is delayed with respect to the other in circuitry, is determined and is used as a measure of the time required by the fluid to traverse the two sensors.
In addition to the additional requirements of providing an ultrasonic signal at each sensor sight, the circuitry described in Critten et al is quite complex.
General purpose signal correlators such as the so-called SAICOR instrument, have been used for extracting flow signals using correlation techniques. These are laboratory instruments, however, and are quite expensive. They must be shared between several flow meters in a large installation to be economically feasible.